In the prior art, there is developed a trailing-type radiation inspection system, such as inspecting systems for van container which are manufactured by Smiths Corporation of U.K. and by Aerospace Corporation of U.K. respectively from the early of 1990. In the above inspecting systems, a fixed radiation source and an array detector are arranged in an inspection passage which can shield radioactive source, the radioactive source emits X-rays of high energy and the array detector receives the X-rays passing through containers in which objects to be inspected are loaded. A vehicle carrying the containers thereon is trailed to pass through the inspection passage by a special trailing unit, when the containers on the vehicle pass through X-rays emitted by the radioactive source, the X-rays passing through the containers are transmitted to the array detector, a density distribution of the objects loaded in the containers is obtained based on variations of intensity of the X-rays, thus obtaining a perspective view of the objects loaded in the containers by converting intensity of the X-rays into gradation of image. With the trailing apparatus of the above inspecting systems, an inspection passage thereof has a length of 60 m, and two additional portions outside of both ends of the inspection passage have a length of 40 m respectively, so that the trailing unit is huge, and the land area required by the trailing unit will be equivalent to that of a soccer court. Such an inspecting system used in Wen Jin Ferry of China and imported from Germany is operated in a circularly trailing mode using three underground tractors. However, the inspecting system is very complex due to overground and underground operations of the tractors. In addition, when a tractor trails a vehicle carrying containers to be inspected, front wheels of the vehicle may slide on the tractor, which shall lead to the vehicle sliding off the tractor, thus causing impact damage to a front axle of the vehicle and strike on a guard gate of the inspecting passage. Therefore, it is known from the above that the inspecting systems in the prior art have the following disadvantages: building projects occupy a large land area, overground and underground projects are very complex, cost of the inspecting system is high, there is accident potential and it is difficult to shield the radiation and to maintain the inspecting system.